During fabrication of microelectronic devices, thin films and metal alloys are deposited on substrates and used as electrical conductors, adhesion layers and diffusion barriers. For instance, the ionized physical vapor deposition (iPVD or ionized PVD) process has been utilized in semiconductor processing for metallization and forming interconnects. Other techniques are used for metallization, for example, chemical vapor deposition (CVD) and atomic layer deposition (ALD) processes. These techniques are utilizing metallic precursors to deposit a metallic layer over the structure. In many cases these methods use plasma source techniques to ionize and excite gas and precursors, since it has been found to be an effective and simple tool to generate high-density plasma (for instance, plasma enhanced CVD, referred to as PECVD, and plasma enhanced ALD, referred to as PEALD).
Typically, the metallization PVD process is performed in a vacuum chamber by creating the metal vapor flux from the metal source (usually a magnetron sputtering source, evaporation source, precursors, etc.). The metal atoms may be transported directly to the substrate or undergo thermalization within a processing zone, depending on the background argon pressure. Eventually, the metal is ionized by a secondary plasma source to provide metallic ions for required process performance. Metal ions and atoms are diffusing towards the wafer surface and ions are accelerated by sheath voltage (potential difference between plasma and wafer potential). Concurrently with this process the metal (either neutral or in ionic state) is transported to other hardware surfaces in the chamber as well, since the processing zone is always surrounded and enclosed by the chamber walls, shields, secondary plasma source interfacing surface, etc. Thus the metal is also ultimately deposited onto the chamber wall and hardware surfaces. This might have an effect on tool performance and mean time before maintenance (MTBM).